The present invention relates to automatic filling machines wherein empty cartons are conveyed along a path while being filled with liquid and sealed, and more particularly to liquid dispensing units for such machines.
High speed automatic filling machines such as is disclosed in U.S. Pat. No. 4,448,008, have been used for filling cartons with liquids, such as milk and juices. These filling machines are required to dispense a predetermined quantity of liquid in each carton as it advances through the filling section of the machine.
One type of dispensing unit that has been used is a double bellows type apparatus such as that disclosed in U.S. Pat. No. 4,402,461. This patent discloses a dispensing unit having a pair of bellows interconnected by an activator sleeve containing a valve that controls the flow of fluid from the upper bellows to the lower bellows. A discharge valve is mounted at the lower end of the lower bellows. The actuator sleeve is mounted for reciprocating movement in an axial direction, and the end of each bellows that is connected with the sleeve moves with it. The opposite ends of the respective bellows are held stationary, so that the axial movement of the body in one direction compresses one of the bellows and expands the other.
An hydraulic or pneumatic ram vertically raises the actuator sleeve causing the upper bellows to contract while simultaneously expanding the lower bellows. This action opens the central valve in the sleeve and pump liquid from the upper bellows into the lower bellows. The ram then lowers the activator sleeve which expands the upper bellows while simultaneously contracting the lower bellows. A spring on the control valve causes the valve to close. This allows the upper bellows to be refilled with liquid from the supply pipe at the top of the upper. The increase in pressure in the lower bellows acts on the discharge valve to overcome the force of the return spring so that the discharge valve opens to allow the liquid to flow from the lower bellows into a carton. The sequence is then repeated sequentially transferring liquid from the supply source into the upper bellows, then into the lower bellows, and finally into individual cartons, as they move past the discharge valve.
Since these dispensing units are used primarily for food products, such as milk, or other dairy products, the unit must be cleaned thoroughly after each use. If the flow passages in the dispensing unit have shoulders or irregular surfaces, there is a risk that some of the liquid or food product may be trapped on these surfaces. Furthermore, if there are springs or other obstructions in the interior of the dispensing unit, it is difficult to clean. Since health regulations require these filling machines to be thoroughly cleaned every day they are used, it is important that the structure of the dispensing unit facilitate the cleaning and sterilization process.
To facilitate cleaning of the dispensing unit, it is desirable to provide for complete draining of the liquid from the system. To accomplish this, any valves in the dispensing unit must remain open during the draining process.
When the system is being filled with liquid product, before starting to fill cartons, any air in the system must be purged to avoid introducing bacteria into the cartons. With prior systems, the air has been removed by operating the dispensing unit while supplying liquid to the unit. The first several cartons that are filled are then discarded, since air is entrained in the liquid contents of the carton. This is a wasteful way to purge the air.
Another important requirement for these dispensing units is that the volume of liquid that is dispensed into each carton must be accurately controlled, so that the carton is not overfilled. Excess liquid may wet the adhesive surface and interfere with sealing of the carton.
It has been proposed to use these dispensing units for food products that contain chunks or particles in a liquid, such as soups. In order to accommodate these chunks or particles, the flow path for the liquid must be free of obstructions, and the valve openings must be large enough that the chunks or particles are not trapped as they are being dispensed.